1. Field of the Invention
The present invention relates to a data backup method and system applied to a system having a plurality of data processors connected to each other through data transmission lines. For the system to which the present invention is applied, when the data processor is a POS terminal for managing sales registration information, the system serves as a point-of-sale (hereinbelow, referred to as POS) system.
2. Description of the Related Art
In the POS system, data processors disposed in stores and the like are connected to a server having a data totalizing function through transmission lines (communication lines). Sales data (POS data) generated in each data processor is transmitted to the server in real time. The server receives the sales data from the respective data processors and then totalizes the sales data. The server totalizes the sales data every predetermined service day in accordance with the regulation of the store. In some cases, the server manages the sales data and attendance data as master data.
In the POS system having a plurality of POS terminals connected to each other through transmission lines, a master terminal and a backup terminal are arbitrarily or fixedly set in order to back up sales data. The master terminal and the backup terminal store data in common. However, if the master terminal or backup terminal goes down due to a failure, data cannot be recovered. Consequently, in the POS system, the other POS terminals cannot call pending sales data and perform an attendance checking process.
Various proposals have been made in order to solve the abovementioned problems. For example, Japanese Unexamined Patent Application Publication Nos. 63-118860,10-124377, 2000-305831, and 2001-93047 disclose improved methods similar to the following method. According to the method, a plurality of units (POS terminals) having the same functions concurrently execute data processing and accumulation. In other words, data processing and accumulation are distributed and executed through the units. Therefore, if a system goes down, the backup and recovery of data can be ensured.
In the system according to the above method, all of the POS terminals have to share data with each other, namely, store data in common in order to realize the recovery of data. If the data accumulation space of each POS terminal is tight, however, it is difficult to construct the above-mentioned backup system.
On the other hand, in some cases, the style or scale of a store utilizing the POS system, or the style of an organization controlling such stores is changed for reasons of business management. In this case, it is not easy to adapt a data backup function to the above change without changing the fundamental structure of the system.